The present invention relates to a series of new macrolide compounds which are derivatives of certain known milbemycin and avermectin derivatives. These compounds have valuable acaricidal, insecticidal and anthelmintic activities. The invention also provides methods of preparing these compounds and compositions and methods for using them.
The milbemycins are a series of macrolide compounds known to have anthelmintic, acaricidal and insecticidal activities. Milbemycin D was disclosed in U.S. Pat. No. 4,346,171, where it was referred to as "Compound B-41D", and milbemycins A.sub.3 and A.sub.4 were disclosed in U.S. Pat. No. 3,950,360. These compounds may be represented by the formula (A): ##STR1## in which R.sup.1 represents a methyl group, an ethyl group or an isopropyl group, these compounds being designated as milbemycin A.sub.3, milbemycin A.sub.4 and milbemycin D, respectively. For the avoidance of doubt, formula (A) also shows the numbering of positions of the macrolide ring system applied to those positions most relevant to the compounds of the present invention.
Subsequently, various derivatives of the original milbemycins have been prepared and their activities investigated. For example, epoxy milbemycins have been disclosed in Japanese patent applications Kokai (i.e. laid open to public inspection) No. 57-139079, 57-139080, 59-33288 and 59-36681 and in U.S. Pat. No. 4,530,921. 5-Esterified milbemycins have been disclosed in U.S. Pat. No. 4,201,861, No. 4,206,205, No. 4,173,571, No. 4,171,314, No. 4,203,976, No. 4,289,760, No. 4,457,920, No. 4,579,864 and No. 4,547,491, in European Patent Publications No. 8184, No. 102,271, No. 115,930, No. 180,539 and No. 184,989 and in Japanese patent applications Kokai No. 57-120589, 59-16894 and 61-180787.
Like the milbemycins, the avermectins are based upon the same 16-membered ring macrolide compound. The avermectins are disclosed, for example in J. Antimicrob. Agents Chemother., 15(3), 361-367 (1979). These compounds may be represented by the formula (B): ##STR2## in which R.sup.1 represents an isopropyl group or a sec-butyl group, these compounds being designated as avermectin B.sub.1b and avermectin B.sub.1a, respectively.
22,23-Dihydroavermectins B.sub.1a and B.sub.1b may be obtained by reduction of the double bond between the 22 and 23 positions and are disclosed in U.S. Pat. No. 4,199,569.
We have now discovered that certain esterified and epoxidized derivatives of these milbemycins and avermectins have unexpectedly potent acaricidal, insecticidal and anthelmintic activities.